We calculate an object's acceleration based on its mass and the force acting upon it,
calculate its velocity based on its acceleration,
then calculate a new position for the object based on its velocity.

Okay. What's this about the Solar System, then?

ISAAC can simulate star systems given a simple set of specifications. So we built a model of the Solar System with it.

Change the Gravitational Constant. Fiddle with the mass of things. See how things react.